1. Field of the Invention
The present invention relates to a structural frame and foundation for buildings.
2. Description of the Prior Art
Principal footings and foundations used in residential construction have, from early times, been vertical extensions of exterior load bearing walls. These extensions below grade vary from shallow 100% brick or concrete trench fill, such as found in traditional English construction, to simple wooden poles or stone columns used in more primitive lands, and the deep footings demanded by cold climates such as in Canada. Unstable soil due to the presence of moisture has also presented footing problems.
These traditional footings and foundations have provided a stable structure, but in relation to the load carried are usually over-designed. Their cost is becoming a significant factor in the overall cost of a house, primarily due to the large volume of material and hours of labour involved. For instance, a typical 8-inch basement wall of concrete having a total perimeter of 130 feet will have a load support capability of 12 million pounds depending on the soil conditions. On the other hand, a typical house, taking into consideration snow and wind loads, sitting on such a foundation, would have a total load of 200,000 pounds. Accordingly, such a conventional foundation is over-designed in a ratio of 60:1. On the other hand, even with this thickness of wall, not enough material is present for proper insulating requirements.
In the prior art, a number of patents have been found which show spaced-apart beam arrangements for footings. Examples of these are Italian Pat. No. 554,796, which issued in 1957, and U.S. Pat. No. 3,470,660, Van Der Lely et al., 1969. Both of these patents which use spaced-apart beams are not practical in areas of high thermal or climatic variations, such as in the tropics or northern regions. For instance, in northern regions, ground movements below the beams of the above-mentioned patents, caused by frost in the ground, would render the foundation system described impractical. In hot and dry climates, the open crawl space is a disadvantage in that heat will collect under the house and rodents will appreciate the cover. U.S. Pat. No. 3,468,094, Campbell, 1969, would not be necessarily affected by frost conditions since footings 27 are set below the frost line. However, the system described in the Campbell patent includes pretreatment of the ground as well as provisions of large deep footings 27 as well as the very large support beams 31. Again, it is believed that the Campbell patent foundations are over-designed, much in the same way as peripheral basements are. Further, the Campbell patent lacks stability in terms of resistance to wind.
In a published report entitled "Mass-Produced Foundations for Mass-Produced Houses," A Progress Report, September 1971, published by the Virginia Polytechnic Institute & State University, there is described a so-called bent beam and column with each composite beam and column including a beam section with a pair of columns extending from each end thereof at a slight angle outwardly and which are adapted to be inserted in the ground. A plurality of such composite beams and columns are spaced apart in parallel arrangement to support a small house. Again, no consideration is provided for extreme climatic conditions wherein frost may cause the columns of the bent beam to move and the house supported thereon to heave. This system also lacks stability in the sideways direction.
U.S. Pat. No. 3,543,459, Mills, 1970, shows a slab foundation construction having a peripheral damming skirt which prevents roots and water from attacking the slab. Once again, uninsulated slab foundations are not practical in northern regions since even with the skirt provided, frost might reach at least the peripheral areas of the ground underneath the slab causing the slab to heave.
The above-mentioned beam foundations and footings suffer structurally in terms of sideways stability. In very warm tropical climates, they also do not have the same benefit as peripheral foundations where such foundations act as insulating barriers to prevent overheating of the house by preventing the warm daytime air from circulating underneath the house.